Points 1 and 2 a directly related.
Transiting at slow speed while submerged reduces detection range but increases the amount of time they can stay dived because of less battery consumption.
Using fudge numbers for game time:
Submerged SM at 3kts could stay submerged for 10 minutes before their battery health bar is depleted. In-game mechanics would either force the SM to surface or it sinks to the bottom and dies but you'd be almost un-detectable until firing. Or, you can dive and sprint at max speed for ~3 minutes before depleting your batteries but your counter-detection range is large.
Either way, the recharge rate or 'cool down' is the same depending on the state of the battery.
Probably too much involved for an arcade game and every player would be terrible at them, or complain or whatever.

I'd challenge the damage inflicted at high end ranges being used as proof of talent. Hitting a target outside 7km has little to do with skill, almost nothing to do with skill actually, unless you break it down into vessel type also.
Hitting a Carrier at 7-10km much easier than hitting a fast moving destroyer which is mostly a case of pure luck.

As soon as your target alters 20 degrees all the target data you have 'calculated' is void.
Another point, if your weapon range is 7km - why this game uses a land distance measurement is beyond me.. - try not to fire at enemy that are outside of 4/4.5 km away. Firing long range, straight running weapons is pure luck if you hit anyway.

Incorrect. It takes experience and mathematics.
Firing many torpedoes down a narrow strait was a classic case of water space denial with any scored tonnage a bonus.
But considering this isn't a simulator you brought up a completely irrelevant reference to a RL scenario.